In motor driven assemblies, transmissions or systems, there are a number of variables for detecting defects. Torque is a key variable for detecting defects, failures and calculation of service life. It is know that precise torque measurements can be made by use of strain gauges of various conventional types to measure the elastic twisting or bending of bushings, shafts, flexible beams and the like. In these systems, however, it has been found that it is always necessary to modify the output or drive mechanism of the system. Further, these methods have been found to be quite expensive because of the need for sensitive amplifiers. Additionally, they are subject to error because of the many environmental parameters which effect accuracy.
Also, force-measuring bearings are used in applications where the load is in a radial or axial direction. These bearings are also provided with strain gauges and require similar sensitive components to process the measurement values. Asynchronous electric motors are widely used for power take-off, because they are cheap, compact and in most in most instances can be connected directly to the power grid.